Poor power quality may cause various problems in electrical power networks. The power flow should preferably have a pure sinusoidal waveform and it should remain within specified voltage and frequency tolerances. In today's electrical networks, deviations from these ideal conditions are frequent due to increasing non-linear and other loads, which disturb the power network.
Waveform distortion may be caused e.g. due to thyristor power control, which utilizes phase-fired power regulation. Deviations from the ideal sinusoidal waveform may also be caused e.g. by rapidly fluctuating loads such as arc furnaces, and welding devices.
A distorted current waveform may be difficult or impossible to correct by using only passive electrical filters.
A distorted waveform may be decomposed into spectral components. In particular, the waveform may be represented as a sum of harmonic components. The waveform distortion may be at least partially compensated by suppressing harmonic components.